The present invention relates to heat exchange between gases, particularly to total heat exchange elements used for heat as well as moisture exchange and to a method of their preparation.
Metal foils or screens have been used in matrixes as the total heat exchange elements for heat exchangers (hereinafter referred to simply as heat exchange elements) to carry out the exchange of heat or moisture between gases. However, elements using paper made from asbestos, fiber glass, ceramic fibers, etc. have great capacity to hold hygroscopic materials for forming moisture exchange abilities, they are light and further they are excellent in that they display a high degree of service durability even when used in the heat exchange of gases containing acidic components. Upon investigating this from the aspect of hygroscopic material it will be found that in addition to lithium chloride and silica gel, molecular sieves are also used as described in Japanese Patent Application Laid Open No. 54-19548. In comparison to those using lithium chloride as the hygroscopic material, heat exchange elements using molecular sieves show superior results in such points as:
1. they have little deterioration in their hygroscopic capacity over time; PA1 2. since there is little deterioration in their hygroscopic capacity upon regeneration, even when directly using city gas as the combustion gas, regeneration can be accomplished with less heat energy required; PA1 3. they don't get wet with liquid even when treating very humid air.
They are also clearly superior in that there is very little deterioration over time, even in comparison to those elements using silica gel as the hygroscopic material.
However, in cases where paper, which has the many advantages as mentioned above, is to be used as a carrier, conventional heat exchange elements using molecular sieves were the result of a process of mixing the paper making materials and the molecular sieve particulates and then making the paper sheets from this mixture. However, they would not display the moisture absorbing capabilities that could be expected from the amount of molecular sieve carried, perhaps because the molecular sieve agglomerates during the paper making stage thereby forming coarse secondary particles.